National Geographic : 1946 Nov
The National Geographic Magazine &(National Geographic Society 1 inlay Dy \ ineri!1i IoIeIIClln Thick Granite Walls Kept Helgoland from Crumbling into the Sea Caves and grottoes indent the cliffs of the west coast, pounded by heavy waves. Once, geologists believe, the Frisian Islands were part of the European mainland. When they were cut off, Helgoland was five times as large as it is today. Before Germany owned it, shrinkage amounted to about half an acre every ten years. By ringing the island with granite imported from Denmark's island of Bornholm, the shrinkage was greatly reduced. Later the Germans also girdled the island with giant iron chains to help hold it together.